A novel synthesis of 2-arylbenzimidazoles in molecular sieves-MeOH system and their antitubercular activity.

Arylbenzimidazoles have been synthesized as antimycobacterial agents. An efficient synthesis has been developed for 2-arylbenzimidazoles from o-phenylenediamines and aromatic aldehydes in molecular sieves-methanol system. The methodology is straightforward to get 2-arylbenzimidazoles (3a-3z) in excellent yields with high chemoselectivity over 2-aryl-1-benzylbenzimidazoles (4a-4z). All these benzimidazole analogues were evaluated against M. tuberculosis in BACTEC radiometric assay. The compounds 4y and 4z exhibited potential antitubercular activity against M. tuberculosis H37RV, MIC at 16 µM and 24 µM respectively. The best compound of the series i.e. compound 4y was well tolerated by Swiss-albino mice in acute oral toxicity. Compound 4y possessing a diarylbenzimidazole core, can further be optimized for better activity.

Synthesis of pharmacologically important naphthoquinones and anticancer activity of 2-benzyllawsone through DNA topoisomerase-II inhibition.

Naphthoquinones are naturally occurring biologically active entities. Practical de novo syntheses of three naphthoquinones i.e. lawsone (1), lapachol (2), and ß-lapachone (3b) have been achieved from commercially available starting materials. The conversion of lapachol (2) to ß-lapachone (3b) was achieved through p-TSA/Iodine/BF3-etherate mediated regioselective cyclisation. Further, 2-alkyl and 2-benzyllawsone derivatives have been prepared as possible anticancer agents. Four derivatives exhibited significant anticancer activity and the best analogue i.e. compound 21a exhibited potential anticancer activity (IC50=5.2µM) against FaDu cell line. Compound 21a induced apoptosis through activation of caspase pathway and exerted cell cycle arrest at S phase in FaDU cells. It also exhibited significant topoisomerase-II inhibition activity. Compound 21a was found to be safe in Swiss albino mice up to 1000mg/kg oral dose.